Atomic interferometric accelerometers use two counter-propagating lightwaves with differing frequency to divide and recombine atomic waves, and to read out their phase shifts due to inertial forces. In a large lab-scale system, these lightwaves can be directed via mirrors through opposing windows of a vacuum chamber that contains the atomic waves. This beam-path adds significant additional size, weight, and cost to the system, as well as increasing sensitivity to vibrations. A proven practice is to introduce both lightwaves through the same window, and then retro-reflect them both from a mirror in order to generate the necessary counter-propagating beams, as this approach also reduces interferometer phase noise. Unfortunately, this approach by itself creates two competing interferometers formed by the two sets of counter-propagating lightwaves or beam pairs. Thus, it is necessary to select only one of the two beam pairs in order to avoid competition between the two beam pairs that would degrade bias and scale factor (SF) stability.
In order to select only one pair of laser beams, a technique has been demonstrated in lab-scale systems in which velocity is imparted to the atom waves prior to initiating the interferometer cycle. This additional velocity induces a Doppler shift in the atom/light interaction, and breaks the symmetry between left-going and right-going lightwaves, making it possible to tune the laser frequencies such that only one pair of lightwaves is resonant with the atoms. However, this technique is difficult to implement in a small or miniature atomic interferometric accelerometer, since it requires additional lasers and because the imparted velocity reduces the time available for interrogation of the atoms.